Genetics Basics

Question 1

[Gen/Basic]

Pleiotropic

Answer 1

Genes that produce many effects
Eg. Marfan affects eyes, heart and skeletal

Question 2

[Gen/Basic]

Locus heterogeneity
Allelic heterogeneity

Answer 2

“locus heterogeneity” refers to when mutations in different genes (at different loci) lead to the same disease
“allelic heterogeneity” describes when different mutations within the same gene (at the same locus) produce a similar phenotype

Question 3

[Gen/Basic]

Epistasis

Answer 3

A genetic phenomenon where the effect of one gene is modified by the presence of another gene

Question 4

[Gen/Basic]

Penetrance vs Variable Expressivity

Answer 4

**Penetrance **
Whether or not a gene is expressed
Can be complete (100%) or incomplete (for example, 50% when only half of people with the gene have the trait)
Expressivity
How much a trait affects a person
Can range from complete to minimal, or it may not be present
Can vary between individuals with the same genotype

Question 5

[Gen/Basic]

Definition of Hemizygous vs heterozygous

Answer 5

Hemizygous - having one copy of a gene
Heterozygous - having two different copies

Question 6

[Gen/Basic]

Product of Mitosis

Answer 6

Two diploid daughter cells

Question 7

[Gen/Basic]

Product of Meiosis

Answer 7

Four haploid daughter cells

Question 8

[Gen/Basic]

Phenomenon achieved by X inactivation?

Answer 8

Dosage compensation
A mechanism by which species with sex chromosomes ensure that the homogametic sex does not have too much or the heterogametic sex too little activity of loci on the homogametic sex chromosome.

Question 9

[Gen/Basic]

When X inactivation occurs?

Answer 9

2 weeks after fertilization

Question 10

[Gen/Basic]

High carrier disease in Ashkenazi Jewish population (5)?

Answer 10

1. Gaucher (GBA) 1/15
2. Cystic fibrosis (CFTR) 1/29
3. Tay-Sachs (HEXA) 1/30
4. Familial Dysautonomia (IKBKAP or ELP1) 1/32
5. Canavan disease (ASPA) 1/40

Question 11

[Gen/Basic]

Formula for mutation rate

Answer 11

μ=
number of new mutations / total number of gamets (2 x newborns)

Question 12

[Gen/Basic]

The relationships that has the coefficient of inbreeding (F) = 1/4
(50% shared genes) (2)

Answer 12

1. Full siblings
2. Parent - child

Question 13

[Gen/Basic]

The relationships that has the coefficient of inbreeding (F) = 1/8
(25% shared genes) (3)

Answer 13

1. Half-siblings
2. Grandparent - child
3. Uncle - niece

Question 14

[Gen/Basic]

The relationships that has the coefficient of inbreeding (F) = 1/16 (3)

Answer 14

1. First cousins
2. Great-grandparent - child
3. Half-uncle - niece

Question 15

[Gen/Basic]

Answer 15

2/3